2,141,012 research outputs found

    Protein import into chloroplasts: new aspects of a well-known topic

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    Protein import into plant chloroplasts is a fascinating topic that is being investigated by many research groups. Since the majority of chloroplast proteins are synthesised as precursor proteins in the cytosol, they have to be posttranslationally imported into the organelle. For this purpose, most preproteins are synthesised with an N-terminal presequence, which is both necessary and sufficient for organelle recognition and translocation initiation. The import of preproteins is facilitated by two translocation machineries in the outer and inner envelope of chloroplasts, the Toc and Tic complexes, respectively. Translocation of precursor proteins across the envelope membrane has to be highly regulated to react to the metabolic requirements of the organelle. The aim of this review is to summarise the events that take place at the translocation machineries that are known so far. In addition, we focus in particular on alternative import pathways and the aspect of regulation of protein transport at the outer and inner envelope membrane

    Soil degradation: a threat to developing-country food security by 2020?

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    Global population in the year 2020 will be a third higher than in 1995, but demand for food and fiber will rise by an even higher proportion, as incomes grow, diets diversify, and urbanization accelerates. However this demand is met, population and farming pressure on land resources will intensify greatly. There is growing concern in some quarters that a decline in long-term soil productivity is already seriously limiting food production in the developing world, and that the problem is getting worse. Sarah Sherr first focuses on the magnitude and effects of soil degradation. She then addresses soil degradation in the future and ends her brief with policy and research priorities.Soil degradation Developing countries., Food security Developing countries.,

    Soil Composition

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    Soil is essential for life on Earth. It is needed for food, air, clothing and so much more. Discussion topics include the terms 'soil', 'dirt', and 'sediment', factors affecting the formation of soils, soil horizons, and the twelve orders of soils. In a hands-on activity, students will collect soil samples from three different locations, use online resources to determine texture and particle makeup, and record their observations. Educational levels: Undergraduate lower division, High school

    Laboratory test for EPB tunnelling assessment:results of test campaign on two different granular soils

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    Earth Pressure Balanced shields are currently the most utilized tunnelling machines throughout around the world. The possibility of using conditioning agents that change the mechanical and hydraulic behaviour of a soil, changing it into a plastic paste and thus permitting soil pressure applications at the tunnel face, is the key point to explain the increasing utilization of this technology. Despite its great importance, not much laboratory researches can be registered on soil conditioning, particularly for cohesionless soils. The conditioning criterion is usually defined on the basis of a trial-and-error procedure developed directly at the job sites. A test that is able to simulate the extraction of soil from the bulk chamber with the screw conveyor inclined upwards, as in real machines, can offer a quantitative indication of the conditioned soil behavior for EPB use. The characteristics of the device and the results obtained on many different types of soil are discussed in order to point out the great importance and quality of results that can be achieved using the proposed test devic

    Chemical enhancement of soil based footwear impressions on fabric

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    This study investigates the enhancement of footwear impressions prepared with soils from different locations on a variety of fabric surfaces with different morphology. Preliminary experiments using seventeen techniques were carried out and the best responding reagents were evaluated further. Results indicated that the soils investigated (a cross-section of soils from Scotland) are more likely to respond to reagents that target iron ions rather than calcium, aluminium or phosphorus ions. Furthermore, the concentration of iron and soil pH did not appear to have an effect on the performance of the enhancement techniques. For the techniques tested, colour enhancement was observed on all light coloured substrates while enhancement on dark coloured fabrics, denim and leatherette was limited due to poor contrast with the background. Of the chemical enhancement reagents tested, 2,20-dipyridil was a suitable replacement for the more common enhancement technique using potassium thiocyanate. The main advantages are the use of less toxic and flammable solvents and improved clarity and sharpness of the enhanced impression. The surface morphology of the fabrics did not have a significant effect on the enhancement ability of the reagents apart from a slight tendency for diffusion to occur on less porous fabrics such as polyester and nylon/lycra blends

    Soil Chemical Properties Under Conservation Agriculture and Cereal-Based Cropping System in Eastern Tarai of Nepal

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    Field experiments were conducted for four years (2014-2017) at five locations namely Salbani, Bhokraha, Simariya, Bhaluwa and Kaptanganj of Sunsari district to assess the changes in soil chemical properties under conservation agriculture (CA)-based practices in two cropping systems namely rice-kidney bean-maize at Salbani and rice-wheat at rest of the locations. In rice-wheat cropping system, there were four treatments: (1) conventional tillage (CT) for rice transplantation and subsequent wheat sowing, (2) conventional tillage rice transplantation followed by zero tillage (ZT) wheat, (3) unpuddled rice transplantation followed by zero tillage wheat, (4) zero tillage in both rice and wheat. Similarly, in rice-kidney bean-maize cropping system, there were four treatments; (1) conventional tillage for rice transplantation and sowing of both kidney bean and maize, (2) conventional tillage rice transplantation followed by zero tillage in both kidney bean and maize, (3) unpuddled rice transplantation followed by zero tillage in both kidney bean and maize, (4) zero tillage in all three crops. Soil samples were taken at initial and every year after rice harvest.The soil samples were analyzed for total nitrogen, available phosphorus, available potassium, pH and soil organic matter.Total nitrogen (N) showed a slightly decreasing trend in the first three years and showed a slight increase at the end of experiment under ZT in all locations. The total N under ZT changed from 0.12 to 0.13%, 0.05 to 0.06%, 0.10 to 0.12%, 0.11 to 0.08% and 0.09 to 0.13% in Salbani, Bhokraha, Simariya, Bhaluwa and Kaptanganj, respectively.  All locations showed the positive values of available potassium; Salbani  revealing considerable change of 64.3 to 78.5 mg/kg in CT while 68.4 to 73.3 mg/kg in ZT condition. The treatment where rice was transplanted in unpuddled condition and zero tilled to wheat, had a mean value of available phosphorus and potassium as 87.3 and 81.9 mg/kg respectively. Soil pH ranged from 4.8 to 7.1 in CT while it was 5.2 to 6.8 in ZT across the locations. The change in soil organic matter in CT of all locations except Salbani was narrower as compared to ZT

    Saprotrophic soil fungi to improve phosphorus solubilisation and release. In vitro abilities of several species

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    Modern agriculture is dependent on phosphate rock (PR), which is a nonrenewable resource. Improvement of phosphorus (P) availability for crops in agricultural soils represents a key strategy to slow down the depletion of PR. The aim of this study was to identify potential P biofertilisers among saprotrophic fungal species. We tested 30 fungal strains belonging to 28 taxa (4 Zygomycota and 24 Ascomycota) and with different life strategies. The study showed that many saprotrophic fungi have the ability to mobilise P from insoluble forms according to a variety of mechanisms. Our results expand the pool of P solubilising fungal species, also suggesting a new solubilisation index and shedding light on parameters that could be basic in the selection of efficient soil P-biofertilisers fungi. Rhizopus stolonifer var. stolonifer, Aspergillus niger and Alternaria alternata were found to be the best performing strains in terms of amounts of TCP solubilisation

    Self help in soil conservation

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    Land is regarded by many people as the symbol of permanence - as a solid asset to pass on to succeeding generations. But farmers know, or should know, that soil is not static. They know that erosion by water and wind can cause good soils to become wastelands, and that wise land use can initially poor soils into expanses

    Prediction of soil available phosphorus based on soil organic carbon

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    There are many cases in which it is desirable to determine relationships among some soil physical and chemical properties. In soil studies, soil available phosphorous (AP) are often determined using laboratory tests, but it may be more suitable and economical to develop a pedotransfer function which uses some easily available soil properties. In this study, a pedotransfer function for predicting soil AP from soil organic carbon(OC) was suggested and soil AP was estimated as a function of soil OC. The soil AP predicted from the soil AP pedotransfer function was compared to the soil AP determined by laboratory test using the paired samples test and the Bland-Altman approach. The soil AP predicted by the soil AP pedotransfer function was not significantly different from the soil AP determined by laboratory test (P>0.05). The mean difference between the soil AP pedotransfer function and laboratory test was 1.57 ppm (95% confidence interval: -2.88 and 6.03 ppm; P = 0.453). The standard deviation of the soil AP differences was 7.01 ppm. The statistical results of the study indicated that the soil AP pedotransfer function provides an easy, economic and brief methodology to estimate soil AP and in order to predict soil AP based on soil OC the pedotransfer function AP = 0.7927 e 4.9922 OC with R2 = 0.92 can be recommended
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